1. Field of the Invention
The present invention relates to an electric rotating machine of the segment connection type including U-shaped conductor segments fitted into slots of its stator core and connected to one another at a side of one of end surfaces of the stator core with respect to an axial direction to thereby form a stator coil.
2. Description of Related Art
An electric rotating machine having a segment connection type stator coil formed by a plurality of conductor segments (may be simply referred to as “segments” hereinafter) made of insulated rectangular wire, which are fitted into slots of its stator core and sequentially connected to one another, can be made smaller in size and weight than a conventional electric rotating machine having a wire-wound type stator coil, because the segment connection type stator coil allows the stator to have a high conductor space factor, and allows the coil ends to have a short axial length.
Such an electric rotating machine having the segment connection type stator coil (may be referred to as “segment connection type electric rotating machine” hereinafter) is described in Japanese Patents No. 3118837 and No. 3196738, and Japanese Patent Applications Laid-open No. 2003-348780, and Laid-open No. 2000-166149, for example. In forming the segment connection type stator coil, two leg parts a U-shaped segment are separately inserted into two slots apart from each other by a distance equal to a pole pitch of a rotor, and then portions of the leg parts protruding from the slots are bent in the circumferential direction in order to join the tip ends of the leg parts to each other.
The U-shaped segment has a head part and two leg parts. Each one of the leg parts has an in-slot conductor portion situated within a slot, and a protruding portion protruding from the slot and bent in the circumferential direction. The head parts of the U-shaped segments make coil ends of the stator coil at a side of one of the end surfaces of the stator core with respect to the axial direction, while the protruding portions of the leg parts of the U-shaped segments make coil ends of the stator coil at a side of the other of the end surfaces.
The segment connection type stator coil is formed by star-connecting or delta-connecting phase coils as many as the number of the phases. Each of the phase coils is constituted by a plurality of the U-shaped segments sequentially connected to one another at their protruding portions (may be referred to as “U-shaped segment continuum” hereinafter), an I-shaped leading segment connected to the leading end of the U-shaped segment continuum, and an I-shaped terminating segment connected to the terminal end of the U-shaped segment continuum.
The portion of each of the leading segment and terminating segment protruding from the slot is bent so as to extend in the circumferential direction for a length equal to half the pole pitch as in the case of the protruding portion of the U-shaped segment. The two slots into which the leading segment and terminating segment are inserted, respectively, are distant from each other by the pole pitch.
This configuration makes it possible to avoid a neutral point and a power supply lead from becoming obstacles in connecting the U-shaped segments at their leg-side coil ends, because the neutral point and the power supply lead can be situated at the side of their head-side coil ends. The leading segment is extended to a connector as a power supply lead where it is connected to an external cable supplying electric power.
Each of the slots has an even number of conductor holding spaces therein which are aligned in the radial direction. Two leg parts of one U-shaped segment are held separately in two conductor holding spaces having different radial positions. The leading segment and terminating segment are also held in two conductor holding spaces having different radial positions.
The U-shaped segment continuum can be constituted by a plurality of the U-shaped segments occupying radially adjacent two conductor holding spaces. In this case, one of the two leg parts of one U-shaped segment protruding from a first conductor holding space of one slot is bent so as to extend by half the pole pitch in the circumferential direction, and one of the two leg parts of another U-shaped segment protruding from a second conductor holding space of another slot distant from the above one slot by the pole pitch is bent so as to extend by half the pole pitch in the opposite circumferential direction. These two leg parts are connected to each other at their tips (protruding ends) opposing with each other. The U-shaped segment continuum having such a configuration may be referred to as “two-layer type U-shaped segment continuum” hereinafter. The leading segment and the terminating segment of the two-layer type U-shaped segment continuum are individually held in two conductor holding spaces having different axial positions.
In another example, the U-shaped segment continuum can be constituted by a plurality of the U-shaped segments occupying radially adjacent four conductor holding spaces. The U-shaped segment continuum having such a configuration may be referred to as “four-layer type U-shaped segment continuum” hereinafter.
One example of the four-layer type U-shaped segment continuum includes a large-sized U-shaped conductor segment (may be referred to as “large segment” hereinafter) and a small-sized U-shaped conductor segment (may be referred to as “small segment” hereinafter). The large segment is inserted into the first one (the innermost one) and the fourth one (the outermost one) of the radially adjacent four conductor holding spaces, and the small segment is inserted into the second one and the third one of the radially adjacent four conductor holding spaces.
The tip portion (protruding portion) of the leg part of the large segment protruding from the innermost conductor holding space is bent so as to extend by half the pole pitch in the circumferential direction. The tip portion (protruding portion) of the leg part of the small segment protruding from the second conductor holding space is bent so as to extend by half the pole pitch in the circumferential direction. These tip portions of the large and small segments are connected to each other.
The tip portion (protruding portion) of the leg part of the large segment protruding from the outermost conductor holding space is bent so as to extend by half the pole pitch in the circumferential direction. The tip portion (protruding portion) of the leg part of the small segment protruding from the third conductor holding space is bent so as to extend by half the pole pitch in the circumferential direction. The tip portion of the large segment protruding from the outermost conductor holding space and the tip portion of the small segment protruding form the third conductor holding space are connected to each other.
In the four-layer type U-shaped segment continuum, since the head part of the large segment is situated so as to cover the head part of the small segment, the leading segment and the terminating segment are inserted into the innermost conductor holding space and the outermost conductor holding space individually.
In a case where each slot has six conductor holding spaces, the two-layer type U-shaped segment continuum and the four-layer type U-shaped segment continuum can be connected in series. In this case, the leading segment or the terminating segment of the two-layer type U-shaped segment continuum is connected to the leading segment or the terminating segment of the four-layer type U-shaped segment continuum. Alternatively, if they are replaced by a special U-shaped segment, the two-layer type U-shaped segment continuum and the four-layer type U-shaped segment continuum can be directly connected to each other.
In a case where the slot has eight conductor holding spaces aligned in the axial direction, two four-layer type U-shaped segment continua can be connected in series. In this case, the leading segment or the terminating segment of one of the two four-layer type U-shaped segment continua is connected to the leading segment or the terminating segment of the other of the two four-layer type U-shaped segment continua. Alternatively, if they are replaced by a special U-shaped segment, the two four-layer type U-shaped segment continua can be directly connected to each other.
To generalize, if the slot has 4n+2 conductor holding spaces (n being a positive integer), the series-connected structure of the two-layer type U-shaped segment continuum and/or the four-layer type U-shaped segment continuum can be used.
If the slot has eight conductor holding spaces, four two-layer type U-shaped segment continua connected in series, or two four-layer type U-shaped segment continua connected in series can be used. Although they can be connected in parallel, it is preferable to use the series connection in view of reducing the armature current. Since such a series-connected structure of the two-layer type U-shaped segment continuum and/or the four-layer type U-shaped segment continuum are described in detail in the above mentioned patent documents, no further explanation is given here.
Next, an example of manufacturing the above described segment connection type stator coil is explained.
At the beginning, a necessary number of two-forked conductor segments are aligned circumferentially, and thereafter, they are worked to become the U-shaped segments each of which has two in-slot conductor portions distant from each other by the pole pitch, so that they can be inserted into corresponding slots of the stator core at once. The above process can be done by use of two coaxial perforated rings, for example. In this case, the two legs of each of the two-forked conductor segment are separately inserted into two holes of the two rings situated in the same circumferential position, and then the rings are relatively turned around by the pole pitch.
After that, the legs are pulled out from the holes with the head portions of the conductor segments deformed into a U shape being fixed, and are inserted into corresponding slots of the stator core.
Next, the portions of the U-shaped segments protruding from the slots are bent in the circumferential direction. Preferably, the protruding portions are bent such that they extend in the circumferential direction by half the pole pitch. The above bend work can be done by use of two coaxial perforated rings, for example. In this case, the protruding portions of the U-shaped segments are separately inserted into corresponding holes of the rings, and then the rings are turned around by half the pole pitch (or the electric angle of π/2). Finally, welding work of the protruding portions are carried out.
In the electric rotating machine having the segment connection type stator coil, the I-shaped leading segment of each of the phase coils is extended as a power supply lead to a connector box fixed to a motor housing. When the electric rotating machine is of the star-connection type, the I-shaped terminating segment of each of the phase coils is extended in the circumferential direction as a neutral point connecting lead.
The electric rotating machine having the segment connection type stator coil disclosed in Japanese Patent Application Laid-open No. 2003-348780 has a problem in that the outer dimension thereof becomes large, because, in this electric rotating machine, the neutral point connecting lead is taken from the outermost conductor holding space, and the power supply lead is laid between the outermost conductor holding space and a connector disposed on a radially inner side of the stator along the head-side coil ends.
Also, the electric rotating machine having the segment connection type stator coil disclosed in Japanese Patent Application Laid-open No. 2000-166149 has the same problem, because, in this electric rotating machine, the neutral point connecting lead is taken from the outermost or innermost conductor holding space, and the power supply lead is taken from a conductor holding space other than the innermost and outer most conductor holding spaces (may be referred to as “intermediate conductor holding space” hereinafter), which make the axial length of the coil ends large.
In addition, the electric rotating machines disclosed in Japanese Patent Applications Laid-open No. 2003-348780 and Laid-open No. 2000-166149 have a problem in that the neutral point connecting lead may deform to thereby come into contact with the rotor when the neutral point connecting lead is taken from the innermost conductor holding space. On the other hand, when the neutral point connecting lead is taken from the outermost conductor holding space, there arises another problem in that the neutral point connecting lead may interact with the inner surface of the motor housing, which makes motor assembling work difficult.
Furthermore, the bending work of the power supply lead made of rectangular wire has been difficult to perform, since the rectangular wire is hard to bend compared to the round wire having the same cross-sectional area. This lowers the efficiency of the motor assembling work, especially when the connector for connecting the power supply lead to an outgoing cable is provided in the external surface of the motor housing.